\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,scale=1]
  \draw [->](-1,-.5)node[above]{$\alpha$}--(-0.025,-0.025);
  \draw [->](0,0)--node [below]{反冲核}(2,-.2);    
  \draw [->](0,0)--(1.25,1.25)node[below]{p};
  \draw (0,0) [fill=gray] circle (2.5pt);
\end{tikzpicture}
\end{document}